Prolonged in Vivo Residence Times of Antibody Fragments Associated with Albumin

Abstract

Antibody fragments can be expressed at a high level in microbial systems, but they may have limited therapeutic value because they are rapidly eliminated from the body. We demonstrate here that site-specific conjugation or binding of bacterially derived Fab' to the long-lived protein serum albumin allows full retention of the antibody's binding characteristics while imparting the albumin's longevity in vivo. In rats the area under the curve for Fab' conjugated to rat serum albumin was 17-fold greater than for the control of Fab' conjugated to cysteine. Again, a bispecific F(ab')(2) with specificity for rat serum albumin showed an area under the curve about 8-fold greater than did a F(ab')(2) without specificity to albumin. Genetic fusions of scFv to albumin were similarly long-lived and could be expressed in yeast to provide the basis of a cost-effective production system.

Biodistribution and tumor imaging of an anti-CEA single-chain antibody–albumin fusion protein

“…Kidneys (8.1±0.4 %ID/g at 0 hr) and spleen (6.6±0.5 %ID/g at 18 hr) had limited activity. Pharmacokinetic studies showed the [ 125 I]-and [ 111 In]-DOTA-versions had nearly identical blood clearance activity of radiolabel (T 1/2 α≈1 hr and T 1/2 β≈15 hr), which were comparable to the half-lives observed for an anti-TNF scFv-HSA fusion protein [2].…”

“…Since the first three residues of HSA were not visible in the crystal structure, they were deleted rather than fusing the scFv directly to the amino-terminus of the mature HSA as previously reported [2].…”

“…Antibody-derived fusions have been generated by chemical conjugation or as recombinant single chain (scFv) antibody-HSA molecules [2,3]. Alternatively, non-covalent approaches have been developed by incorporating peptides that bind to albumin [4,5] or albumin-binding domains [6] and have been shown to enhance imaging in Her2 positive tumors.…”

Cross-species Binding Analyses of Mouse and Human Neonatal Fc Receptor Show Dramatic Differences in Immunoglobulin G and Albumin Binding

“…Neither molecule shows more than half the serum persistence of endogenous rat albumin (56). Notably, mouse and rat FcRn HCs showed high homology (89%) (supplemental Table 3), as did rat and mouse albumin sequences (90%).…”

Shark variable new antigen receptor biologics – a novel technology platform for therapeutic drug development

“…This has value if the domain is designed to be an in vivo imaging agent where signal--to-noise ratios determine assay sensitivity but can be potentially limiting for the development of an efficacious drug. There are multiple ways to improve the pharmacokinetic profile of small proteins or peptides [69][70][71][72][73][74][75][76][77][78][79][80]. Fusion to an antibody Fc domain, as mentioned previously, is one way [81]; however, if being small is advantageous, then adding multiple extra domains (Fc) counteracts this size benefit.…”